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Collective transitions of two entangled atoms and the Fulling-Davies-Unruh effect
摘要： We calculate respectively, from the viewpoints of an instantaneously/locally inertial observer and a coaccelerated observer, the transition rates of the two-atom system in the symmetric/antisymmetric entangled state [jψ (cid:2)i]. The scalar fields to which the atoms are coupled are respectively assumed to be in the vacuum state and a thermal state in the instantaneously inertial frame and in the coaccelerated frame. We show that both the upward transition jψ (cid:2)i → jgAgBi and the downward transition jψ (cid:2)i → jeAeBi take place, where jgAgBi and jeAeBi represent two collective eigenstates of the two-atom system with both atoms in their ground state and excited state respectively, and the transition rates observed in the two frames are identical only if there exists a thermal bath at the Fulling-Davies-Unruh temperature in the coaccelerated frame. Though both the downward and upward transition rates are characterized by the Plankian factor, this factor does not show up in the average variation rate of energy of the two-atom system, as a result of the perfect cancellation of the terms in the transition rates in the instantaneously inertial frame multiplied by the Plankian factor which corresponds to the Unruh thermal bath, and the cancellation of the temperature-dependent terms in the transition rates observed in the coaccelerated frame. A comparison of the transition rates of a static two-atom system in interaction with the massless scalar field in a thermal state at an arbitrary temperature with those of a uniformly accelerated two-atom system in interaction with the vacuum massless scalar field shows that the equivalence between the thermal bath and the uniform acceleration, which is well known to be valid for the single atom case, no longer holds for the two-atom system in the symmetric/antisymmetric entangled state. The effect of atomic uniform acceleration in the transition rates of the two-atom system, and the roles of both the downward and the upward transitions in the disentanglement of the two-atom system are also discussed.
关键词： Fulling-Davies-Unruh effect,Collective transitions,transition rates,thermal bath,uniform acceleration,entangled atoms
更新于2025-09-23 15:19:57
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Operational Performance and Degradation Influenced Life Cycle Environmentala??Economic Metrics of mc-Si, a-Si and HIT Photovoltaic Arrays in Hot Semi-arid Climates
摘要： Life cycle metrics evolution specific to the climate zone of photovoltaic (PV) operation would give detailed insights on the environmental and economic performance. At present, vast literature is available on the PV life cycle metrics where only the output energies ignoring the degradation rate (DR) influence. In this study, the environ-economic analysis of three PV technologies, namely, multi-crystalline silicon (mc-Si), amorphous silicon (a-Si) and hetero-junction with an intrinsic thin layer (HIT) have been carried out in identical environmental conditions. The energy performance parameters and the DR rate of three PV technologies are evaluated based on the monitored real time data from the installation site in hot semi-arid climates. The assessment demonstrates that the HIT PV module technology exhibits more suitable results compared to mc-Si and a-Si PV systems in hot semi-arid climatic conditions of India. Moreover, energy metrices which includes energy payback time (EPBT), energy production factor (EPF) and life cycle conversion efficiency (LCCE) of the HIT technologies are found to be 1.0, 24.93 and 0.15 years, respectively. HIT PV system has higher potential to mitigate the CO2 and carbon credit earned compared to mc-Si and a-Si PV system under hot semi-arid climate. However, the annualized uniform cost (UAC) for mc-Si (3.60 Rs/kWh) and a-Si (3.40 Rs/kWh) are more admissible in relation to the HIT (6.63 Rs/kWh) PV module type. We conclude that the approach of considering DR influenced life cycle metrics over the traditional approach can support to identify suitable locations for specific PV technology.
关键词： annualized uniform cost,amorphous silicon,crystalline solar cells,life cycle assessment,PV cells,energy payback time,life cycle metrics,HIT,photovoltaic systems,degradation rate
更新于2025-09-23 15:19:57
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A novel optical network model for network burden release and congestion reduction based on passive optical network
摘要： In this article, a new optical network structure coping with network congestion is proposed, which is based on passive optical network, and adopts data storage devices coupled with optical line terminal to release network burden. It is shown by our network performance simulation that this network has many merits such as free-scale, fewer connections, larger clustering coefficient, and smaller average shortest path length in comparison to the passive optical network. The novel network structure can replace the far-end service connections with the near-end ones, reduce congestions in an optical network, and, furthermore, relieve traffic burden in optical backbone and metropolitan area networks.
关键词： duplicate service,uniform content location,complex optical network,congestion reduction,Passive optical network
更新于2025-09-19 17:15:36
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Performance improved tunable millimeter-wave signal generation employing UFBG based AOTF with bit walk-off effect compensation
摘要： A scheme for the generation of mm-wave signals at different frequencies with improved performance is proposed and demonstrated by employing a uniform fiber Bragg grating based acousto-optic tunable filter (UFBG-AOTF). The different frequencies carry different information at a required data rate according to their application. This method reduces the complexity of the system by alleviating the cascaded Mach-Zehnder modulators (MZM) and a good transmission performance can be achieved by the FBG. In the previous system, the distance of transmission is reduced to 15 km due to bit walk-off effect and it also reduces the BER values at larger distances. In the proposed system, the bit walk-off effect is discussed and compensated to increase the transmission distance up to 60 km. The simulation results along with clear eye-diagrams show that the BER values are improved at larger distances than the previous system which proves the performance improvement of the proposed system.
关键词： optical millimeter-wave,radio-over-fiber,bit walk-off effect,acousto-optic tunable filter,uniform fiber Bragg grating
更新于2025-09-19 17:15:36
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[IEEE 2018 International Symposium on Micro-NanoMechatronics and Human Science (MHS) - Nagoya, Japan (2018.12.9-2018.12.12)] 2018 International Symposium on Micro-NanoMechatronics and Human Science (MHS) - Uniform Transfection: Shock Wave Generation in Laser Ablation and Microcontact Printing
摘要： With the increasing need of regenerative medicines, cell therapy, and biopharmaceutical drug, it is necessary to develop a method for massively parallel delivery and uniform transfection. This research explores the possibility of using μCP (using cell adhesive and cell blocking agents) for printing massive number of cells on a substrate and using optoporation methods (nano-second pulsed radiation) to perforate cell membranes. With combining these two methods, a stand-alone micro-device capable of performing localized intracellular delivery will be developed. In this paper, we confirmed the generation of shock wave upon optoporation, tried intra-cellular delivery using Calcein, develop the stamp for micro-contact printing and performed the printing.
关键词： optoporation,laser ablation,uniform transfection,shock wave generation,microcontact printing
更新于2025-09-19 17:13:59
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A Criterion to identify maximally entangled nine-qubit state
摘要： We present a generalized criterion for maximally entangled nine-qubit states, whose minimum averaged subsystem purity should be equal to 1/14. In this note, we prove that the absolutely maximally entangled state for nine qubits does not exist. In other words, we pronounce that the pure (9, 1, 5)2 quantum error-correcting code does not exist. Further, we construct a new genuine nine-qubit maximally entangled states of 110,15 and 1 balanced purities equal to 1/16, 1/8 and 1/4, respectively. We found that the marginal density matrices for subsystems of 1,2,3- qubits all completely mixed in these states; therefore, maximally entangled nine-qubit state is a 3-uniform state.
关键词： 3-uniform states,criterion,maximally entangled nine,-qubit state
更新于2025-09-19 17:13:59
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[IEEE 2019 Photonics North (PN) - Quebec City, QC, Canada (2019.5.21-2019.5.23)] 2019 Photonics North (PN) - Optimization of Nonlinear Optical Properties of Tellurium-Oxide-Coated Silicon Nitride Waveguides
摘要： In low-power wireless neural recording tasks, signals must be compressed before transmission to extend battery life. Recently, compressed sensing (CS) theory has successfully demonstrated its potential in neural recording applications. In this paper, a deep learning framework of quantized CS, termed BW-NQ-DNN, is proposed, which consists of a binary measurement matrix, a non-uniform quantizer, and a non-iterative recovery solver. By training the BW-NQ-DNN, the three parts are jointly optimized. Experimental results on synthetic and real datasets reveal that BW-NQ-DNN not only drastically reduce the transmission bits but also outperforms the state-of-the-art CS-based methods. On the challenging high compression ratio task, the proposed approach still achieves high recovery performance and spike classification accuracy. This framework is of great values to wireless neural recoding devices, and many variants can be straightforwardly derived for low-power wireless telemonitoring applications.
关键词： deep learning,quantized compressive sensing,non-uniform quantization,Wireless neural recording
更新于2025-09-19 17:13:59
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The analysis on simulation and invalidation of hot-spot temperature distribution in micro-defective crystalline silicon solar cells
摘要： According to the distribution of reverse biased leakage current of micro-defective solar cells, the mathematic models of the hot spot thermal power of photovoltaic(PV) modules are established. The uniform and non-uniform distribution of thermal power in hot spot solar cell are theoretically calculated and experimentally analyzed in different shading conditions. Based on the model, the hot spot temperature distribution of different defective cells is simulated by ANSYS software. Then a novel experimental platform is set up to validate the simulation results in outdoor conditions. The mechanism of hot spot failure and the worst hot spot condition are analyzed. According to the results of experiment and simulation, the relative deviation between simulation and experimental data is less than 10% through the model proposed in this paper. Furthermore, in the normal modules, according to the result of simulation and experiment, the worst case of hot spots happens when the heat power is maximum and the shading ratio is about 10-20%. In the defective modules, it happens when the heat power is not maximum and the shading ratio is about 50-60%.
关键词： reliability,non-uniform distribution,Hot spots,micro-defective solar cells
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - An adaptive non-uniform PSK modulation scheme for elastic optical network
摘要： In this paper, we introduce a novel adaptive non-uniform PSK modulation scheme, which is capable of adjusting the amplitude of the constellation points based on the channel condition, so as to achieve flexible signal transmission and reduces the receiver complexity. Simulation results indicate that services with different quality of service (QoS) requirements can be conducted on a single optical signal according to the channel condition. And the system efficiency can be improved to its maximum while guaranteeing the acceptable error rate at the same time. The performance of the proposed scheme exhibits an enormous potential for future high-speed elastic optical network.
关键词： Non-uniform modulation,Elastic optical network,PSK modulation,QoS
更新于2025-09-16 10:30:52
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Sub-carrier Loading Strategies for DCO-OFDM LED Communication
摘要： LEDs, particularly those used for Visible Light Communications (VLC), have a limited bandwidth, while above their 3 dB bandwidth, the roll-off is relatively gentle. If the modulation bandwidth would be limited to the 3 dB LED bandwidth, the achievable rate would be unacceptably constrained. Hence, effective communication systems need to optimize the use of bandwidth significantly above this 3 dB point. Orthogonal Frequency Division Multiplexing (OFDM) is a popular method to fine-tune the amount of power and constellation as a function of the channel response over different frequencies. Various power and bit loading strategies have been proposed and simulated in literature, but their performance was not captured in expressions. This manuscript derives these for optimal waterfilling, uniform and pre-emphasized power loading for the LED channel, that severely attenuates high frequencies. We also investigate the influence of practical discrete constellations and verify our new results experimentally. Interestingly, simple uniform loading only falls less than 1～2% short of the throughput achieved by waterfilling, but when we restrict OFDM to discrete QAM constellation sizes, the penalty for uniform loading is 1.5 dB. Inspired by the good performance of uniform power loading, we propose an algorithm to find the best discrete bit loading for uniform power within an optimized band. As pre-emphasis is nonetheless attractive because a flattened channel does not need adaptive sub-carrier loading, we quantify its penalty. This can be modest provided that the system can adapt its transmit bandwidth, thereby adaptively switching upper sub-carriers to zero power.
关键词： Orthogonal Frequency Division Multiplexing (OFDM),pre-emphasis,power loading strategies,LED channel,QAM constellation sizes,uniform loading,waterfilling,Visible Light Communications (VLC)
更新于2025-09-16 10:30:52